Inside the London Bubble, the media narrative about Jeremy Corbyn
goes a bit like this:

Corbyn has been a
disaster as the new leader of the Labour Party.

He's tearing the party apart
as the socialist army inside the Momentum group threatens
to deselect moderate MPs who show him disloyalty.

He can't control the people
who sympathise with him, like veteran lefty Ken Livingstone,
whom he appointed to his defence review team and who
immediately caused offence by saying Labour's shadow defence
minister Kevan Jones “might
need psychiatric help.”

And, as Business Insider noted previously, Miliband was actually
a successful Labour leader.
He added 740,000 votes to Labour's total at the last
election, compared to the previous one. (Labour lost because
the Tory gains from the Liberals, coupled with Labour's losses to
the SNP, screwed the Labour Party out of about 1 million votes it
would otherwise have got.)

Polls are not elections of course. And the 2020 vote is a long
way away.